Motor control system



Plil 24, w45- G. DAVENPORT MOTOR CONTROL SYSTEM Original Filed Sept. l2,1941 3 Sheets-Sheet 1 Y WW.

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April 24, 1945- G. DAVaNPoRT MOTOR CONTROL SYSTEM Original Filled Sept.l2, 1941 5 Sheets-Sheet 2 nlillllll IllIxJ mw m4.

INVENTOR ATTOR N E Y April 24, 1945 G. DAVENPORT MOTR CONTROL SYSTEM 5Sheets-Sheet 3 Original Filed Sept. 12, 1941 INVENTOR M @ew/ffm huKATTORNEY Patented Apr. 24, 1945 2,374,257 MOTOR CONTROL SYSTEM GrangerDavenport, Montclair, N.

J., assigner to Gould & Eberhardt, Incorporated, Irvington, N. J., acorporation of New Jersey Original application September N0. 410,491.Divided and this 12, 1941, Serial application November 6, 1942, SerialNo. 464,711

6 Claims. (Cl. 172-239) The present invention relates to a. system oimotor controls and interlocks adapted more particularly for machine tooluse,.wherein one or more prime movers may be employed to propel variouselements in transverse directions in sequential order and wherein it maybe desirable that the motions oi the driven element or elements becoordinated and related to perform, in a. given cycle, an operation orseries of operations on a workpiece.

The invention aims to render available asystem of controls forcontrolling the operational characteristics of two motors, selectivelyoperable to effect movement ofthe driven member or members atdifierent'rates selectively in opposite directions along transversepaths of their movement, and wherein operation of one of the motorsautomatically precludes operation of the other. In the example about tobe referred to, the driving transmissions involved embody one or moremechanical clutches and reversers, and at least one of the drive motorsis itself reversible, and the present invention aims to provide acontrol system whereby conflict between the several power drives andreversing means is avoided `so that the operator is assured that themechanisms will operate at the rate and in the direction, as expectedand intended, whenever the control button or other control elementassociated with a particular operation, rate, or direction, is actuated.

In my prior application, Ser. No. 410,491, of which the presentapplication is a division, a worm gear hobbing machine has been taken asrepresentative of a type of machine in which the several motions of thetool and work require esl feed transmission,

pecial directional relations consistent with cutting right and left handworm gears. Such a machine will also be referred to herein for thepurpose of illustrating an environment wherein the present invention iswell adapted. The present invention, it will be understood, is notrestricted to machine tool applications, but is applicable to other usesin which transmissions are utilized in a functionally similar manner.

In the worm gear hobbing machine referred to, the work carrier and hobare power rotated and fed during a normal tooling' operation, and thefeed may be radially relative to the work axis, or tangentially relativeto the work axis, or radially and tangentially, sequentially accordingto the plan of the gear cutting operation. In such a machine there isalso an auxiliary power source, for effecting relative movement betweenthe hob and the work in transverse planesand also in .with certainmechanical opposite directions in each of the transverse planeswhichmust not be used concurrently with the main drive, but when used must bedirectionally controlled in a manner compatible with a previously setcondition in the main drive.

The present invention aims to render available a semi-automatic controlfor motors performing such functions which, in conjunction elements ofthe driven transmission, is operative to prevent incompatible orinconsistent operation of two or more trains of mechanisms and powersources, correlates directional relations of one or more of the powersources with another or with relation to previouslyl set mechanicalelements of the machine, provides for repeated stopping of one or moredrive trains at preset distances, guards against accidental abuse of thecontrols and, in cases where a reversible power source selectivelydrives a particular element or train which is also mechanicallyreversible, insures that the direction of operation of the power sourcewill be in harmony with the required direction of movement of the drivenelement in accordance with a preset condition of the transmission.

In the machine of the type referred to, the main motor drives thecutter, the work, the main transmissions, and the lead gearing, all inharmonious relation'. Revel-sers and clutches are built into the variousdrive trains at selected points so that reversals oi motion may be madein some trains, and directional relations maintained or restored inothers, and still others disengaged. In the same machine an auxiliarysource of power is provided to eiect at least some of the opera.- tionalmovements at a relatively rapid rate for the purpose of expediting thesetting up of new work and for expediting machine movements betweentooling cycles. v

Neither of the two sources of power should be operated while the otheris operating, for obvious reasons, and

- tem of controls wherein each power source is controllableindependently of the other, b ut wherein thecontrol' oi each isinterlocked with and mutually dependent upon the other.

The invention further undertakes to provide a double system of controlsfor a reversible motor which is operable to drive an independentlyreversible transmission in-such manner that when that transmission hasbeen preset to eect a given operation by another motor, one of the twosystems of controls iorvthe reversible motor bethe other system becomesincomes effective and the infeed and tanieed sub-y this invention aimsto provide a sys- 'Y of control System machine illustrated is v motorand' enters the -end of the machine, worm drive train at a gearing 56,56, 59',

condition.

Other objects and advantages will be in part indicated in the followingdescription and in part rendered apparent therefrom in connection withthe annexed drawings.

To enable others skilled in in the various Ways they may embody the samedrawings de-y contemplated by this. invention. picting a typicalembodiment of this invention have been annexed as a part of thisdisclosure and, in such drawings, like characters ofl reference denotecorresponding parts throughoutall the views, of which:

`Figure 1 is a side view of bodying this invention tions of certaininterlocked controls.

a machine tool emthe art so fully to' e apprehend the underlying'features hereof that and illustrating the locathe actual direction ofmotor shaft 1| conveys feed wormwheel mechanism Fig. 2 is a wiringdiagram of a preferred form v for two motors.

Fig. 3 is a schematic diagram thereof.

Fig. 4 is a line diagram of the main drive and rapid traversetransmissions and the interlocking controls.

Fig. 5 is an enlarged view of two of the control levers of the machineand their relationto tions of the motor control systems. f Myaforementioned application sets forth in detail the structure andoperation of the machine disclosed in the drawings. However, forconvenience and to enable a better understanding ofr` the invention tobe attained a condensed description of the machine to which thisinvention is suited will also be given here.-

Referring to Figure provided with a base member 43|) that supports arotatable work table 3| and a` reciprocable stanchion 32 mounted on theways 33. The stanchion carries avertically adjustable slide-34 to whicha head 35 is pivoted. and the latter supports' a laterally movable tool'slide 31 which carries the hob spindle 38 and the hobbingA tool 39. Thevarious elements just mentioned are mountedand-related so that the hobmay' be moved right. up and down, in and out, and angularly about thehorizontal pivot. certain of these movements being useful in setting upthe machine t. and others being used during the tooling operation.

machine begins at the main drive shaft 42 4|, see Fig. 4. Gears shaft 44transmit the change gears 41 and 'I'he main drive for the through thebelt or chain 46, shaft 43, gears 48 and power to aset of speed thenceto the cutte'rdrive gears 49, 60, shaft 6|, gears 62, worm gears 63 andindex plates 64 transmit the power to the hob spindle 33.

The work table drive'is taken ofi.' the cutter point beyond the speedchange gears 41. Gears 65 are provided for this purpose which transmitpower through differential 80, to the shaft 61 and index reversing means3|. A shaft forward to the table driving change speed and 62 conveyspower worm and worm gear 6l and 64. To effect a re- 1, the worm gearhobbing toward the left or toward the.

shaft 48. At the'front versal in the direction of table rotation anidler gear 6| a is adapted to be incorporated in the index gearing GI,but the insertion or removal of theidler does not, it will be seen.eil'ect the dlrection of cutter rotation.

The cutter feed (tangentially and radially) is taken olf the work indextrain by the bevel gears 12, connected beyond the change gears andreversing mechanism 6|, of feed andv rate is initially definitelyrelated to the direction and rate of work rotation. A cross' power tothe worm and 10, thence through shaft 69 to three serially arranged setsof change gears 86, 31. and 68 to a main feed shaft 13. vThese changespeed mechanisms provide 32 different -feed rates. Amain feed clutch 14,when engaged. transmits the feed power to a coaxial shaft 13', v landfrom this shaft 13 the feed power may be directed to the cutter througheither the infeed train ofmechanisms-v feed train of mechanisms 11,controlled by a se lector clutch 15. 'I'he infeed train comprises gears18, 19, shaft 80, gears 8|, 82. and gears". 84 and v82. The final gear82 is slidable on the feed screw shaft 85 and may be shifted to meshwith gear 8| or nut 86 secured to the stanchion 32 cooperates with thefeed shaft to effect cutter movement inv or out by power. Manual meansfor shifting the fstanchion is provided through bevel gears 81 and aYhand crank shaft 98. V When the selector clutch 16 is'shifted to en-Agage with clutch gear 89 and shaft 13" (the cen tripetal.feed train isdisconnected)` and feed power is conveyed to the tangential feed screwI;

91 through bevelgears 8|, reset clutch 92, worm and worm wheel 93, 94,and bevel gears 95 and movements to the cutter when desired.

It maybe mentioned chine is initially constructed to impart a feed chine`is, set up for a fixed relation notwithstanding the fact that themachine may hand o'f worm gears. In other words, if the ma-V A cuttingright-hand worm gears, work rotation wise (Fig. 4), and the tangentialfeed of the hob During tangential feeding, correlation in the relativerates of cutter rotation and work rotation is obtained through thedifferential mecha'- and thus the direction- 16 or a cutter tangential iwith the reversing gear, A

here that the gearing for v the tangential feed of the hob of thepresent mabe set up for cutting either' of the tanfeed and sliding gearstherein as follows:

"the serially arranged feed change mechanisms 08, 61, 68 are selectivelyshifted'by means of |02, shaft |03 to worm and worm wheel |014 connectedwith the differential housing 53. Thus whenever the tangential feedtrain is effective, compensation is automatically made for the lateralshifting of the hob. The direction of compensation, i, e., whetheradditive. or subtractive, is determined by the direction of rotation ofthe ldifferential housing 56, and this is controlled bl! Each of levers56; '61* and 68a.

Themain feed clutch 14 is shiftable from its engaged to its disengagedposition by a shifter 14* operated from a rod 11|b that is geared to theI shaft 14 extending along the side of the ma-l chine and on which issplined afeedand traverse control lever |20. The control shaft 14.cextends through a bracket 32 mounted to the side of the stanchion andthe lever |20 is splined to the shaft and moves with the bracket.' 4

The dual clutch15 is similarly shifted to one 1 of its three positionslby shifter 15* that is actu-- for propelling the cutter the beltorchain avoided and therefore ated by .the rod l".y The latter is gearedto a control shaft c that also extends along the side of the machineandthrough the bracket 32". An infeed and tangential feed control lever |40is splined to the control shaft 15 and is operable to shift the clutch15 fromneutral to either of its effective positions. Spring detent meansindicated at 151 is provided to assist in holding the clutch in setposition.

is us'ed for infeed hobbing only, the

previously set positions of reversers or motion direction restorers inseries therewith. In the instant embodiment of this invention, the needfor naturalizlng directions of two drive trains applies to the infeedtransmission, whereas, as to the tanfeed transmission the motion is notcapable of being changed independently of the motor. However, the motoroperations and resulting movement imparted to the cutter must becompatible with the legends Left and "Right" on the control buttons atall times. In the instant organization, therefore, one motor is utilizedselectively to drive two transmissions; as to the one transmission themotor must automatically adapt itself to a changeable condition therein,but as to 'the other transmission, the mo-.

'tor operations must be consistent throughout;

and as to both transmissions the motor must be capable of being reversedwithout upsetting previously set relations.

The manner in which the several trains of mechanisms and motors areautomatically hary moniously related and interlockedvwill be explainedwith reference more particularly to Figs. 1, 2, and 3, the latter twofigures illustrating the wiring and schematic wiring diagrams,respectively.

'magnetic starter for the' main drive motor Referring to Fig. 2, the boxMS represents a 40, and the box RMS represents-a reversing netic starterfor the rapid traverse motor |05.

Y -Each of the starters is of standard commercial construction and neednot be explained in detail The transmission of this machine alsoincludes at the completion of its'feed' the traverse motor' explained,and inconsistent operations prevented. Furthermore, the direction ofmotion of the reversible motor must be definitely coordinated with thefunctioning of the relation restoring mechanism 00-84 in the infeedtrain, i, e., as the direction of rotation of the feed shaft 13' changeswith the hand of the gear to be cut, the gear 82 in the infeed branchtrain may be shifted in" other condition, and consequently the traversemotor must run forwardly to back travel the cutter in the one instance,and run reversely t0 back travel the cutter in the other. Such asituation is confusing and means have been provided for automaticallycorrelating the motor controls so as to obtain motor operation in such adirection as will be consistent with the legends In and Out on thecontrol buttons irrespective of the tov effect an infeed under the onecondition, and out to effect an infeed under the except to state thatswitches a, b, and c operated by` electric solenoidsl', l* and 3b.Normally, the motor switches are open and no current passes to thehowever, one of the solenoids gized the associated main switch is closedand the motor operation starts.

Each of the solenoids is controlled by a-se'condary circuit'connectedacross power lines L1 and LP as illustrated diagrammatically in Fig. 3.Assuming all of the serially arranged switches in the control circuitfor solenoid l'l are closed, as shown in the diagram, the pressing 'ofthe Start button will energize the solenoid close the main switch a, andstart the motor 40 operating. Connected in parallel with the motor 40 isa coolant motor ||0 which may be operated whenever the main motor isoperating. provided also its own starting switc SW is thrown to closethe circuit.

When the Start button for the main motor is pressed a -holding circuit,marked I and 2 through contact a on the diagrams, is completed aroundthe start button and the latter may be released. In series ahead of theswitch and a Stop switch, both normally closed. A pressing of the Inchswitch will, if the main the motor control main motor has been started,first deenergize the coil l* and open the holding circuit therebystopping the motor, and continued pressing of the Inch switch will closea circuit across lines and 2* thereby energizing coil I* of the startingpanel MS and restart the motor. The starting of the motor by the Inchbutton does not, however, complete any holding circuit across the coilI* and the main motor operates so long as the Inch button is pressed.Ahead of the Inch switch, the Stop switch is placed, and which, whenpressed, will open-any circuit that may have been completed to coil I'Land thereupon effect stopping of the main motor.

mag-

thereof, are controlled andl respective motors. When. Il, 3*, 3b isenerstarting switch 1s an meh precision abutment III mounted upon thedual clutch control rod The abutment III is carried by a short lever H2that maintains a xed angular relation with respect to the shaft 15 sothat a rocking of the shaft 15 for the purpose of actuating the dualclutch 15, will abutment III in or outof operative relation with respectto the operating button of the switch In.

Fig. 5 illustrates in full lines the relative positions of the partswhen the dual clutch is in neutral.

When, however, the lever |40 is moved to its eX- treme downwardposition, the dual'clutch 15 is shifted to the right. in Fig. 4, andpower infeeding of the stanchion will occur. concurrently, the abutmentIII is rocked into the path of movement of the switch In, and when thestanchion has been power fed to the point where the abutment is engagedby the switch In, the control circuit for the main motor is opened,whereupon the motor stops and power infeed stops.

Should the tangential feed train be in operation, the limit switches TFRand TFL are arranged and preset to open the circuit to the main alsoposition the A clutch is disengaged for the forward and reverse coils ofthe reversing starter RMS. Accordingly, when the main power feed clutchis engaged, the rapid traverse motor is inoperative, and it (lever indotted line position in Fig. 5) that the switch RT is closed therebymaking it possible to operate the rapid traverse motor, provided otherconditions are met.

As illustrated in Fig. 3, two sets of parallel circuits are provided forcontrolling the operation of coils 38 and 3h of the reversing panel RMS.One set is arranged to controldirection of motor operation when used forthe purpose of effecting power traverse of the cutter to the the left,and the other set controls motor operation when used for effecting powertraverse of the cutter in or out. Each of these four control motor whenthe cutter reaches the set limit of j travel either to the right or tothe left. The

microswitches TFR and TFL are mounted in the pivotal head of thevmachine,'one at either-side of a short actuating lever H3. Lever H3projects through the front face of the head and has secured thereto ahorizontally extending rod llt that passes through and some distancebeyond each end of the cross slide 31. At each side of the slide 31adjustable dogs H5 are mounted upon -the rod, each of which may be handset to be engaged by the cross slide 31 when the latter has been powerfed tangentially the required distance. When the cutter slide hasreached one of the abutments I I5 continued movement thereof actuatesthe rod Ill and its associated lever IIB and opensv one of the switchesTFR or TFL depending upon whether the direction of power feed is to theright or to the left, respectively.

I'he operator, having previously set the actuating dogs in their properpositions to stop the cutter feed in or to stop the cutter feed to theright or to the left at the proper points, may then press .the Startbutton for the main motor and the machine will tooling cycle and stopautomatically at the end thereof. Or he may Inch the cutter to cuttingposition and then start the normal operation. At any time during theoperating cycle he may stop the machine by pressing the Stop button. Y vInterlocked with the control for the main moytor 40 is the control forthe auxiliary rapid traverse motor I 05. The interlocking of thesecontrols takes the form of a normally closed switch .45 motor, is anormally closedlimit switchV LSR,

LSR and LSL are located in start operatinga'nd perform the circuitsincludes a normally open push button switch marked Right, Left, In andOut," respectively, and to avoid confusion in their manipulation thefour circuits are arranged in pairs and each pair connected to oppositesides of a double throw switch marked TI. Switch TI is in series withthe rapid transverse switch RT and is also mechanically connected withthe dual clutch control lever |40. When the dual control lever |40 isrocked downward, to thereby engage the clutch 15 with the infeedtransmission 19 etc., the switch and completes an electrical connectionto the pairl l -of traverse motor control circuits including the TIcloses one pair of its contacts In out circuits including is renderedVineffective. When, however, the control lever It is shifted to itsuppermost vposipush buttons, and the pair of tion, to engage the tanfeedtransmissions 11 with i the feed lshaft 13', the switch TI is actuatedby 1 an extension |40 on'the lever to a position closing itsother pairlof contactsy and completes a.V

circuit including `the Right and' circuits that portion of the Left"push buttons, and the pair of include the In and "Out buttons becomeineffective.

In series with eachof the manual switches.

Right, Left," In and "Oul'f for the traverse LSL, LSI, LSO, respectiveThe limit switches of the machine adjacent the microswitches previouslyexplained and are adapted to be actuated by the same lever pelled to theright or to the left the set distance. The limit switches LSI and LSOVare mounted upon the base of the machine. in the positions to beactuated by dogs carried by the movable stan- I chion 32 vwhen thestanchion has reachedthe limit of its travel in or out.

- micro limit switches are RT which is mechanically connected for opera-4) and a short extension |268 on the cotrol lever |20 langages anddepresses the button of the y switch RT and opens the entire controlcircuits In the control for vthe in series which automatically compels aback traverse of the cutter at the completion of the feed before thefeed can again be started forward, and

effected only if the main feed clutch is disengaged, whereas, thetangential limit switches for the traverse motor are in cutter can betraversed back and forth by the one motor as often as desired.Ordinarily, however, the cutter slide is traversed to the right or tothe left prior to any actual tooling operation performed by the cutteron completion of the tooling operation and traversis only when the powerfeed right or to the right and left push buttons .the swivel head 35 yH3 concurrently with'the microswitches TFL and TFR. Two sets of switchesin this particular main feed motor, the

back traverse can be parallel, so that the the work or after the ingofthe cutter back and forth when it is out of engagement or out ofcontact with the work will not, of course, injure the workpiece.

It has been explained above that when the rapid traverse motor is usedforv traversing the cutter stanchion in or out the direction ofoperation of the motor must concord .with the previously set position ofthe sliding gear 82 in the infeed sub-transmissiomand the position ofthe gear l! depends upon whether the machine is set up for cuttingleftor right-hand gears. The present invention aims to simplify thecontrol in a manner whereby one set of push buttons marked In and Outmay be used to effect stanchion traverse in the directions indicated bythe legends on the buttons, when the machine is setup for cutting eitherrightor left-handed gears. To achieve that end a pair of .mechanicallyconnected reversing switches SR are connected in the In and "Out controlcircuit o! the motor |05 between the coils 3* and Sband the limitswitches ISI and LSO. When the converting switch SR is in the positionindicated in Fig. 3, -a pressing of the In buttonwill energize theforward coil 3'* of the 'reversing panel and the used at the time fortraversing the cutter to the left or to the right, and in that eventalso driving the differential mechanism 58 through the branch driveIIII, the starting of the main motor.

40 wouldalso drive the differential and bring about a chaotic condition.Therefore, to 'guard against an inadvertent operation .of the main motorwhile using the traversing motor, each of the push button switchesRight, Left, In and Out (marked R, L, I, and O in Fig. 3) are doublecircuit switches. Each of the switches has one set of contacts normallyclosed and connected in series with each of the others and forms part ofthe control circuit for the main motor. Fig.

. 3 illustrates diagrammatically the series lconnection of the traversemotor control switches with the control circuit of the coil I* of themain starting panel MS for the main motor. The dottedl lines in Fig. 3represent the mechanical connection between the respective push buttons(R, L, I, 0,) and their respective series connected switches theyoperate. When, for example, the Right button is pressed to traverse thecutter to the right, an interconnected switch in the conmotor will runin a forward direction, whereas, a

pressing of the Out button will energize the reverse coll 3b and themotor will run in the opposite direction. However, when the switch SR isshifted to its other position, the In button controls the reversing coil3b and the Out" button controls the forwarding coil 3*.

The switch SR is located in the machine ina position to be operatedautomatically when the sliding gear 82 is shifted from one effectiveposition to another. As shown on Figs. 1 and 4, a short lever 82projects laterally `from the gear shifting rod 82b to a positionintermediate the opposed buttons of the reversing switches SR, When therod 82b is shifted to restore a previously existing directional motionin the feed shaft 85, the switch SR is also actuated to 4close theswitches on one side and `complete portions of the controlling circuitto the coils 3a and 3b, and when the control rod is shifted to its otherextreme position the switches are also closed on the other side andthereby complete portion `*of the circuit to the coils 3 and 3b but inthe reverse manner. By interlocking and relating directional rotationsof the traverse motor with the position of the sliding gear 82 in theinfeed transmission.

one set of control buttons may be employed with the assurance that thedirection of cutter traverse will be consistent with the legend on thebutton actuated when .the machine is set up for either rightor left-handgear cutting. It will be further observed on inspection of Fig. 3, thatthe reversing switch SRis inserted in the control v circuit for the inand out motions of the stanchion, and its function is confined solely tothat branch of the control. Such aA device for reversingdirectional-relations is not required in the control circuit for theright and left traverse motions for the reason that directions ofmovement are predetermined by the fixed gearing between `the rapidtraverse motor |05 and the tangential feed screw When-the traverse motor|05 is being operated to propel the cutter in or out or to the rightorto the left, the main motor 4B must not, of `course, be allowed tooperate because a starting of the main motor 40 would cause work andcutter rotations to occur thus bringing about a dangerous condition.Moreover, anddependent upon whether the rapid traverse motor lIll isbeing erse motor at once stops the main drive.' On the trol-circuit ofthevmain motor is opened. Accordingly, if the main motor is running atthe time, a pressing of the Right button of the trav- .other hand if theRight button is being actuated and the traverse motor is operating, thecontrol circuit for the main motor cannot be completed and the motorcannot be started. The same interlocking relation between the controlcircuit vof the main motor and thecontrol circuits forv the reversingmotor is provided with respect to all of the control buttons Right,Left, In or Out and, in respect to the main motor 40, all of the controlbuttons for the traversing motor "l5 are stop switches.

Fig. 2 of the drawings illustrates one method of wiring the machinewherein the various con nections leading to and from the severalswitches and control panels are'l brought into a cable IIB. Inasmuch asallvof the control buttons for both motors are located upon the movablecutter stanchion 32, as illustrated in Fig. 1, the cable H6 is providedwith a flexible portion IIB* between the stanchion mounted elements andthe base mounted elements to provide for the moving of the stanchion. Asimilar flexible portion Ille is provided in the cable IIB between thestanchion mounted elements and the switches in the relatively movablehead 35. Thus the head and the stanchion may move relatively to eachother and to the stationary base of the` machine and the electricalconnections remain intact. The numerals I to 2l in Fig. 2 indicatesimilar connecting lines of the control circuits that lead in or out ofthe cable IIB and correspond in numbering to the system used in Fig. 3for the purpose of clarifying the circuits and their interconnections.

Without further analysis, the foregoing will so characteristicsof eitherthe generic or specific aspects of this invention and, therefore, suchadaptations should be, andare intended to be,

. comprehended within the meaning and range of equivalency of thefollowing claims.

Having thus revealed this invention, I claim as new and desire to securethe following comknowledge, readily Y binations and elements orequivalents thereof. by Letters Patent of the UnitedStates:

.1. A control system for correlating the operation and direction oioperation of a plurality of motors operatively connectible topropel amember combining a rst motor and a reversible second motor, a controllerfor the first motor including a start switch and a plurality of normallyclosed stop switches, a reversing controller for said reversible motor,a forward control switch i'orsaidr controller, a reverse control switchfor said Tcontroller, said start and said control switches each beingelectively operable to eiect associated motor operation; and meansinterlocking each of the said control switches for the reversing motorwith one vof the normally closed stop switches for the said rst motor sothat said rst motor may be operated exclusively or so that saidreversible motor may be operated in either direction exclusively topropel said member.

' 2. A control means for a reversible motor comprising a reversingcontroller, a dual control circuit for the controller including twoparallel connected sets oi' forward and reverse switches, and meanscommon to both of said parallel connected sets of control switches forrendering but one of said sets of forward and reverse switches etiectiveto control forward and reverse motor operation at any one time.

3. The combination set forth in claim 2 including means in the circuitsor one of said sets of forward and reverse switches for oppositelyconverting their normal effect upon the actuation `of said controller tothereby eiect motor operation in directions opposite from normal.

4. A control system for controlling the opera tion oi' atleast twoelectric motors operatively connectible to propel a member, one of saidmo tors being reversible. combining separate control means for each ofsaid motors each adapted when actuated to eii'ect operation of each ofsaid motors in a direction corresponding to the direction normallyeffected on `actuation of the rel0\at will to eiect motor operation in adirection opposite to that normally eil'ected on actuation of itsseparate control means.

5. A system of control for a reversible motor comprising, a forward andreverse controller for the motor for controlling its direction ofoperation, manually operable means normally eilecA tive when operated toactuate said controller and eect forward operation of said motor,manually operable means normally eiective when actuated to actuate saidcontroller and eiect reverse operation of said motor, and additionalmeans for reversing the eiective action of said two manually operablemeans on said controller whereby to cause motor operations directionallyopposite to said normal directions of operation respectively when saidmeans is actuated.

6. A system of control for a reversible motor comprising, a. manuallyoperated normally for- 'ward motor switch, a manually operated normallyreverse motor switch, means responsive to the actuation of said manualswitches to eiect motor operations normally in correspondence, andelectively operable means interposed between said two manual switchesand said responsive means for converting the responsive action of thelatter thereby to eii'ect reverse motor operation when said normallyforward switch is actuated, and forward motor operation when saidnormally reverse switch is actuated.

' GRANGER DAVENPORT.

